Over the past 3 or 4 years, it has become clear that extracellular vesicles (EVs) play a far more important role in patient physiology than previously thought. There are now numerous examples of studies showing that EVs have a role in cell-cell communication in neuronal cells, may be involved in drug transport across the blood-brain barrier, and impact a variety of signaling mechanism because it is known that EVs can cross the blood brain barrier. The fundamental problem which is the most common thread in the entire literature, is that EVs are hard to isolate, difficult to identify, very difficult to quantitate, and providing classification information is very time consuming and costly. EVs are defined as being from 10-150 nm ? far below the diffraction limit of optical systems and therefore too small to image without the aid of electron microscopy. This proposal presents a technology that is unique in that it can create an electronic signature of EVs and translate that into a pseudo image with precise details in the spatial domain. It can quantitate particles and provide a distribution analysis but this distribution is based on single particle measurement, not bulk measurements like dynamic light scatting. The technology is based on the principle of reflective phase grating (RFG), a technology never before applied to biological systems, but regardless is a mature and low cost technology that can be mass produced as it has for the Blu-ray technology. There are four key features of RFG technology; particle resolution approaches 10nm, analysis takes minutes not hours, particles can be measured in liquid phase, and material cost per sample approaches $1 so the potential impact on research and clinical diagnostics is enormous. We propose to add a fluorescence detector within the confines of this application which will provide origin classifier information, critical to understanding the impact EVs have on physiology.